Variations of Inheritance Chapter 10.3 Variations of Inheritance

Intermediate Inheritance

Sometimes neither allele is dominant, so the offspring are a mixture intermediate inheritance– mix of alleles Ex. Andalusian chickens NOT BLENDING

Multiple Alleles

Sometimes there are more than just 2 alleles Example is blood type with A, B, and O They get written as IA, IB, i (with A and B being dominant to O) codominant – when dominant alleles share expression, like blood type AB (IA and IB)

Polygenic Inheritance

Examples are height and skin color Example: If multiple genes affect a phenotype, it is called polygenic inheritance Examples are height and skin color Example: 3 genes for height A, B, C are tall a, b, c are short. You can be AABBCC and be tall, AaBBCC is less tall, AaBbCC is less tall, etc. Some characteristics – dozens of genes

Importance of Environment

The environment can affect the phenotype of genes leaves on a plant – might change every season based on conditions identical twins – may have different physical activity, medical history, exposure to sunlight, etc.

Concept Check 10.3 Question 1 For a trait with intermediate inheritance, what is the phenotypic ratio for F2 offspring of a monohybrid cross? How is that different from a simple dominant-recessive cross?

Concept Check 10.3 Answer 1 1 : 2 : 1 In a simple dominant-recessive cross the phenotypic ratio would be 3 : 1.

Concept Check 10.3 Question 2 Two parents have type O blood. What blood type would you expect for their first child?

Concept Check 10.3 Answer 2 Type O

Concept Check 10.3 Question 3 What is the likely mechanism of inheritance for a characteristic with a large range of phenotypes? Explain.

Concept Check 10.3 Answer 3 Polygenic inheritance The potential combinations of alleles increase with the number of genes affecting a characteristic.

Concept Check 10.3 Question 4 Give three examples of human physical characteristics affected by the environment.

Concept Check 10.3 Answer 4 Height, build, shade of skin, blood count